Additive manufacturing and mechanical testing of interpenetrating metal composites
Topic(s) : Material science
Co-authors :
Frederik SIEGMUND (GERMANY), Joél SCHUKRAFT (GERMANY), Kay André WEIDENMANNAbstract :
Additive Manufacturing (AM), commonly referred to as 3D printing, is a promising technology that is transforming traditional manufacturing paradigms. Although AM has widespread applications across various industries, the additive manufacturing of metals is a particularly transformative field. It employs advanced methods to produce metal parts layer by layer, providing higher design adaptability, minimized material waste, and improved manufacturing efficiency. By arranging multiple materials in a three-dimensional interpenetrating manner, functional and structural characteristics can be combined flexibly, leading to enhanced mechanical and thermal properties.
Literature reports the successful production of multi-material parts from two different metals using selective powder deposition and selective laser melting. Customized, highly efficient cooling solutions made of copper and steel are primarily produced. However, intermetallic phases with undesirable properties can form between the different metals when the powder is melted. Additionally, the process cannot be used to create closed hollow structures. Moreover, it is currently uncommon to change the material within a single layer, which enables the production of interpenetrating structures.
In the field of ceramic materials, approaches for using fused filament fabrication (FFF) for interpenetrating composites are already known. The authors have transferred this to interpenetrating metal composites. The filament used is similar to pellets in metal injection molding (MIM) and consists of a thermoplastic matrix, which is filled to a high degree with metal powder. The two-step debinding and sintering process converts the green body into an interpenetrating metal composite without passing through the molten phase. This results in a fully metallic part with interlocked metals. The approach allows interpenetrating structures with a minimal wall thickness of 0.21 mm and layer heights of 0.12 mm.
Although each metal has its own preferred sintering parameters, a composite of two materials can only be sintered using a single sintering program. Furthermore, the sintering temperature must be below the melting temperature of the lower melting metal. To prevent cracks, the combined materials may have to be adjusted in terms of shrinkage and sintering temperature in the future.
Mechanical testing was conducted on different minimal surface structures, including gyroid, Schwarz-P, and Schwarz-D, each consisting of a 1:1 ratio of copper and steel. The purpose was to investigate how the structure affects the mechanical properties. Prior to testing, micrographs of the manufactured structures were prepared to identify flaws and cracks that occurred during sintering due to the different shrinkages mentioned above. The influence of the microstructure and its pre-damage were compared to the obtained mechanical properties.
Literature reports the successful production of multi-material parts from two different metals using selective powder deposition and selective laser melting. Customized, highly efficient cooling solutions made of copper and steel are primarily produced. However, intermetallic phases with undesirable properties can form between the different metals when the powder is melted. Additionally, the process cannot be used to create closed hollow structures. Moreover, it is currently uncommon to change the material within a single layer, which enables the production of interpenetrating structures.
In the field of ceramic materials, approaches for using fused filament fabrication (FFF) for interpenetrating composites are already known. The authors have transferred this to interpenetrating metal composites. The filament used is similar to pellets in metal injection molding (MIM) and consists of a thermoplastic matrix, which is filled to a high degree with metal powder. The two-step debinding and sintering process converts the green body into an interpenetrating metal composite without passing through the molten phase. This results in a fully metallic part with interlocked metals. The approach allows interpenetrating structures with a minimal wall thickness of 0.21 mm and layer heights of 0.12 mm.
Although each metal has its own preferred sintering parameters, a composite of two materials can only be sintered using a single sintering program. Furthermore, the sintering temperature must be below the melting temperature of the lower melting metal. To prevent cracks, the combined materials may have to be adjusted in terms of shrinkage and sintering temperature in the future.
Mechanical testing was conducted on different minimal surface structures, including gyroid, Schwarz-P, and Schwarz-D, each consisting of a 1:1 ratio of copper and steel. The purpose was to investigate how the structure affects the mechanical properties. Prior to testing, micrographs of the manufactured structures were prepared to identify flaws and cracks that occurred during sintering due to the different shrinkages mentioned above. The influence of the microstructure and its pre-damage were compared to the obtained mechanical properties.